Gene flow between crops and their wild relatives has long influenced the dynamics of wild populations.  With the introduction of transgenic crops, concerns emerged regarding the possibility for increased invasiveness in wild populations.  Studies of hybridization and estimates of the fitness of crop-wild hybrids relative to their wild counterparts have allowed us to understand which crop-wild complexes might be most vulnerable to such changes.  Further, studies of important life history stages and selective responses have improved our understanding of how population dynamics and population genetics could jointly affect the outcome.  Through these studies we have developed an understanding that ecological interactions within populations may well affect the process of introgression of crop alleles in wild populations.   Previous studies identified alterations in life history characteristics of crop-wild sunflower hybrids including greater emergence, larger seedlings, and a greater likelihood of survival to reproduction, along with lower seed production.  The relative fitness of crop-wild hybrids has also been shown to increase considerably under stressful conditions, such as competition. 

Results/Conclusions

In the work reported here, we present data on the wild plants in the study, in particular the relationship of early life history characteristics to survival and reproduction in sunflowers grown in realistic, high-density populations with ratios of hybrids and wilds expected in high and low gene flow scenarios.  Wild plants in the high gene flow population produced fewer seeds and had reduced survival to reproduction compared to plants in low gene flow populations, possibly indicating that greater numbers of hybrids create a more challenging or competitive environment for the wilds.  The actual values of these fitness components varied across maternal families, with survival ranging from 0-29% and seed production ranging from 3-58 seeds per plant.  Early life history characteristics showed interesting variation as well.  Most seedlings emerged over a 25 day period, but the proportion of seedlings that emerged from each population ranged from 30-78%.  Days to emergence and seedling size appear to be related to fitness components indicating selection on these early stages.  These results can help us understand how competitive interactions and possible alterations of life history with hybridization may ultimately affect the potential for crop gene introgression into wild populations in crop-wild hybrid zones.